add sysupgrade script for config preserving system upgrades. only implemented for x86-2.6 at the moment, but can be ported to other platforms easily

SVN-Revision: 8456

target/linux/x86-2.6/base-files/default/lib/upgrade/platform.sh

@@ -0,0 +1,27 @@
+platform_check_image() {
+	[ "$ARGC" -gt 1 ] && return 1
+
+	case "$(get_magic_word "$1")" in
+		48eb) return 0;;
+		*)
+			echo "Invalid image type"
+			return 1
+		;;
+	esac
+}
+
+platform_do_upgrade() {
+	get_image "$1" > /dev/hda
+	sync
+}
+
+x86_prepare_ext2() {
+	# if we're running from ext2, we need to make sure that we have a mtd 
+	# partition that points to the active rootfs partition.
+	# however this only matters if we actually need to preserve the config files
+	[ "$SAVE_CONFIG" -eq 1 ] && return 0
+	grep rootfs /proc/mtd >/dev/null || {
+		echo /dev/hda2,65536,rootfs > /sys/module/block2mtd/parameters/block2mtd
+	}
+}
+append sysupgrade_pre_upgrade x86_prepare_ext2